The US, tipping, and claiming tips on expenses

Question

In the US tipping is not an option. What is the best way of covering yourself with regards to HMRC and not being out of pocket on a business trip to America? Do you add 10% to your receipts and hope for the best? Or should you allow a per diem and hope that a daily allowance will cover your living expenses?

Answer

+1 on this question, we have to travel to the USA for a trade show once a year and this confused me as there didn’t seem to be any kind of official information available!